I’m only familiar in dealing with this in humans but my instinct is saying you can treat the same... maybe try a warm soak or warm q tip and gently help loosen it up?
I would place a warm wet washcloth compress on the eye for a few minutes while holding her to soften the crusts. Clean it out with saline, and get some Terramycin eye ointment from your feed store. Do you see any sneezing, bubbles in the eye, or nasal drainage? It’s possible the chick’s eye was pecked, but look for signs of a respiratory infection.